A variety of techniques have been developed to control fuel flow into a combustion chamber of an internal combustion engine. These techniques are generally described as rate shaping techniques, which provide varying methods of controlling rates of fuel flow into a combustion chamber. By reducing the rate of fuel flow during an initial portion of an injection event, NOx formation is reduced. The fuel flow rate is then increased or unrestricted during the latter portion of the injection event. However, dividing an injection event into a first portion with a first fuel flow rate and a second portion with a second, higher fuel flow rate increases the total length of an injection event, which increases fuel consumption and decreases engine efficiency.